1. Field of the Invention
The present general inventive concept relates to a spitting method to maintain a printhead in an array-type inkjet image forming apparatus.
2. Description of the Related Art
An inkjet image forming apparatus forms an image by ejecting ink from a shuttle-type inkjet printhead reciprocating in a main scanning direction perpendicular to a transfer direction (sub-scanning direction) of paper. The inkjet printhead includes a nozzle unit having a plurality of nozzles which eject ink. Recently, attempts have been made to realize high speed printing by using, instead of a shuttle-type inkjet printhead, an inkjet printhead having a nozzle unit having a length corresponding to the width of the paper in the main scanning direction. In an array-type inkjet image forming apparatus, since an inkjet printhead is fixed and only the paper is being transferred, simple and high speed printing can be performed.
An array-type inkjet printhead includes a great number of nozzles. For example, to print an image on A4 size paper, with a resolution of 600 dpi (dot/inch) in a main scanning direction, about 4960 nozzles are required. In general, an inkjet image forming apparatus of an array-type performs a spitting operation to keep the nozzles in an optimal printing condition by ejecting ink through the nozzles before or after printing. However, since an array-type image forming apparatus includes a much greater number of nozzles than a shuttle-type image forming apparatus, a large amount of ink is consumed due to spitting of nozzles in the array-type image forming apparatus.